This essay contends that the documentary method of interpretation in ethnomethodological studies as it has been developed since the founding work of Garfinkel contains a basic ambiguity that has not been sufficiently explored. Garfinkel's key concepts of reflexivity and et cetra practice have been misinterpreted by those who subsequently developed the field of ethnomethodology. Reflexivity incorrectly has been taken to mean the relation between act and social structure, and et cetra practice as that which fills the gap between act and rule.<br> Yet, this paper argues that the original potential of Garfinkel's work lies within the ways in which some things are made visible and others invisible through the mechanism of reflexivity, and the ways in which rules are made through et cetra practices. If reflexivity and et cetra practice are not understood in these terms, we miss the ambiguity within the documentary method of interpretation operates as a form of ideology and that both are essential to sense-making but nonetheless are a illusion.